Accident Overview
On October 18, 2015, at 0745 central daylight time, a Beechcraft 23, N2339J, operated as an instructional flight under 14 CFR Part 91, was substantially damaged during a forced landing near Humboldt Municipal Airport (M53) in Humboldt, Tennessee. The flight instructor and student pilot were not injured. Visual meteorological conditions prevailed, and no flight plan was filed.
Preflight and Flight
According to reports, the student pilot conducted a preflight inspection, confirming oil quantity of 6 quarts and fuel quantity of 33 gallons. The fuel was strained and appeared normal. After the flight instructor arrived, they verified the oil and fuel quantities again. The preflight and engine start were normal, and they taxied to the active runway for takeoff. At approximately 950 feet above ground level, the engine began to lose power and sounded like it was "missing," according to the student pilot. The engine was producing partial power.
Forced Landing and Post-Accident Inspection
The flight instructor took over the controls, checked the fuel, magnetos, and applied carburetor heat, but no improvement was noted. He turned right back toward the departure airport to avoid a residential area north of the airport, performed S-turns to lose altitude, and intended to land on runway 22. However, seeing a highway near the arrival end of runway 4 and the risk of landing long, he elected to land in a bean field. During the landing roll, the nose landing gear sheared off after striking an incline, causing the nose to strike the ground. Federal Aviation Inspectors examined the airplane and noted substantial damage to the engine firewall.
The airplane was recovered for detailed examination. A compression check showed all cylinders except the No. 2 cylinder had compression above 72 psi; the No. 2 cylinder produced only 8 psi. Further inspection revealed carbon deposits on intake and exhaust valve seats and faces, and the No. 2 cylinder intake valve did not seat fully due to deposits. The No. 2 cylinder exhaust pipe flange was separated from the cylinder exhaust seat face by about 0.25 inch on the outer left side, and the stud was missing the nut and both washers.
The right magneto was inoperative; disassembly revealed a failed permanent magnet breaker end bearing and six missing teeth from the large distributor timing gear. The No. 2 cylinder spark plugs were tested: the top plug tested satisfactorily, while the bottom plug tested marginally with weak spark and lead deposits on the electrode.
The annual inspection of the airframe and engine was completed on May 15, 2015. At that time, the engine and airframe had accumulated 3,082 hours total time, and the engine had 861 hours since the last major overhaul. About 31 hours had been flown since the annual inspection.